Which level is characteristic of the strength of the evidence provided by the results of a quasi-experimental study?
A. Level I
B. Level II
C. Level III
D. Level IV
Correct Answer: C. Level III
Evidence provided by quasi-experimental studies is level III. Evidence obtained from well-designed controlled trials without randomization (i.e. quasi-experimental). Levels of evidence (sometimes called hierarchy of evidence) are assigned to studies based on the methodological quality of their design, validity, and applicability to patient care. These decisions give the “grade (or strength) of recommendation.”
Option A: Level I evidence is obtained from a systematic review of all randomized, controlled trials. Evidence is from a systematic review or meta-analysis of all relevant RCTs (randomized controlled trial) or evidence-based clinical practice guidelines based on systematic reviews of RCTs or three or more RCTs of good quality that have similar results.
Option B: Level II evidence is obtained from at least one well-designed randomized, controlled trial. Evidence is obtained from at least one well-designed RCT (e.g. large multi-site RCT).
Option D: Level IV evidence is obtained from nonexperimental studies. Evidence is from well-designed case-control or cohort studies. In level V, evidence is from systematic reviews of descriptive and qualitative studies (meta-synthesis). In level VI, evidence is from a single descriptive or qualitative study. Lastly, in level VII, evidence is from the opinion of authorities and/or reports of expert committees.